Molecular phylogenetics and evolutionary history of ariid catfishes revisited: a comprehensive sampling

While the topologies obtained support the monophyly of basal groups, up to ten genera validated in previous morphological studies were incongruent with the molecular topologies. New World ariines were recovered as paraphyletic and Old World ariines were grouped into a well-supported clade that was further divided into subclades mainly restricted to major Gondwanan landmasses. A general area cladogram derived from the area cladograms of ariines and three other fish groups was largely congruent with the geological area cladogram of Gondwana. Nonetheless, molecular clock estimations provided variable results on the timing of ariine diversification (~105-41 mya).This study provides the most comprehensive phylogeny of sea catfishes to date and highlights the need for re-assessment of their classification. While from a topological standpoint the evolutionary history of ariines is mostly congruent with vicariance associated with the sequence of events during Gondwanan fragmentation, ambiguous divergence time estimations hinders assessing the vicariant hypothesis on a temporal framework. Further examination of ariid fossils might provide the basis for more accurate inferences on the timing of ariine diversification.The catfish order Siluriformes is a very diverse natural group that occurs primarily in freshwater. Catfishes are widespread and their distribution encompasses all continents, even Antarctica, as evidenced by Eocene-Oligocene fossils [1]. The order includes 36 extant families and over 3000 valid species plus an estimated ~1500 undescribed species [2,3]. Several morphological and molecular studies have addressed the relationships among catfish families [e.g., [4-6]] and recent evidence indicates that large basal clades are restricted to particular continental masses, suggesting a long history of intercontinental isolation [6]. Thus, catfishes offer an exceptional opportunity for studying evolutionary and biogeographic trends. The fossil record of Siluriformes is r